Generally a double clutch transmission implies a transmission having two clutch devices therein. A double clutch transmission generally receives torque input from an engine selectively at its two input shafts using two clutches. The double clutch transmission then changes the torque and speed using gears on the two input shafts, and outputs the chosen torque and speed.
Such a double clutch transmission has been devised basically to compactly provide a multi-speed transmission of higher than five speeds. The two clutches and synchronizing devices included in a double clutch transmission may be controlled by a controller, and accordingly, such a double clutch transmission may also realize an automated shift gear (ASG) that eliminates the necessity of a driver's manual shifting.
A clutch included in a double clutch transmission may be categorized as a dry-type clutch or a wet-type clutch based on its operation. A dry-type clutch utilizes the same principle as a clutch device conventionally disposed between an engine and a manual transmission. A wet-type clutch utilizes the same principle as a clutch device inside an automatic transmission.
A wet-type clutch generally has a higher torque capacity than a dry-type clutch. Therefore, for an engine of high output power, a wet-type clutch is appropriate. In order to stably transmit a high output torque of a high powered engine, the widths of the gears in the transmission must be large. Therefore, a double clutch transmission designed for a high torque engine may easily become very large.
However, double-clutch transmissions that address the above drawback have a reverse driven gear that axially corresponds to a drive gear on the input shafts. In such a case, a diameter of the reverse driven gear is limited by the corresponding drive gear so that a reverse speed may only have very small reduction ratio relative to a first speed.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known in this country to a person of ordinary skill in the art.